1. Field of the Invention
The present invention relates to workpiece engaging tools used in manufacturing operations and, specifically, to hemming devices for forming a hem between two or more workpieces.
2. State of the Art
In manufacturing operations, various types of tools are employed to engage workpieces and/or to perform work on such workpieces. Typically, grippers and clamps are used to engage workpieces at the completion of one manufacturing operation and to remove such workpieces from one work station for subsequent transport to another work station or to a storage location.
In a typical stamping operation in which metal sheets are progressively formed to a final shape through a series of work operations in adjacently disposed stamping presses, grippers are employed to remove the metal sheet from each press and, in combination with additional parts handling equipment, to deposit the workpiece in an adjacent press or an intermediate idle station located between adjacent presses.
Typically, such grippers are formed of a number of interconnected pins and links which effect opening and closing of gripper jaws. Such mechanisms are complicated in construction and high in cost. Further, the pins and links of such grippers are employed to drive the gripper jaws into a position engaging the workpiece. This provides an inefficient and variable force to grip such workpieces.
In hemming applications, such as the manufacture of vehicle doors, deck lids, etc., the edge of one sheet of metal is bent around the edge of an adjacent disposed sheet to form a hem joining the two metal sheets together. Typically, a complex and elaborate machine is employed to bend the edge of one sheet around the edge of the adjacent sheet. Such machines utilize a complex arrangement of fluid cylinders and links to effect the bending of the metal edge or flange.
It would be desirable to provide a workpiece engaging apparatus for manufacturing operations which has a high workpiece engaging force and, yet, is simple in design. It would also be desirable to provide a workpiece engaging apparatus for manufacturing operations which can provide an infinite pressure to a workpiece. It would also be desirable to provide a workpiece engaging apparatus for manufacturing operations which simplifies a hemming application in which the edge of one sheet of metal is bent around the edge of another sheet of metal.